A United Airlines jet uses pre-conditioned air to cool the interior before take-off at Seattle-Tacoma International Airport on Aug. 13, 2013.

A United Airlines jet uses pre-conditioned air to cool the interior before take-off at Seattle-Tacoma International Airport on Aug. 13, 2013.

Photo: Port Of Seattle

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A worker attaches a hose to carry pre-conditioned air to a jet at Seattle-Tacoma International Airport on Aug. 13, 2013.

A worker attaches a hose to carry pre-conditioned air to a jet at Seattle-Tacoma International Airport on Aug. 13, 2013.

Photo: Port Of Seattle

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A hose carries pre-conditioned air to a jet at Seattle-Tacoma International Airport on Aug. 13, 2013.

A hose carries pre-conditioned air to a jet at Seattle-Tacoma International Airport on Aug. 13, 2013.

Photo: Port Of Seattle

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A plant generates pre-conditioned air for jets at Seattle-Tacoma International Airport on Aug. 13, 2013.

A plant generates pre-conditioned air for jets at Seattle-Tacoma International Airport on Aug. 13, 2013.

Photo: Port Of Seattle

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Sea-Tac centralizes heating and cooling of parked jets

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Traditionally, airplanes have used auxiliary engines to cool or heat their cabins, burning jet fuel in the process. Seattle-Tacoma International Airport just launched a better system.

The airport built a central plant that "pre-conditions" air, then sends it through 15 miles of pipes to each of the 73 gates.

"This long-range investment by the airport will save money for the airlines, reduce our carbon footprint, clean the air of emissions and reduce noise for our neighbors," Elizabeth Leavitt, the airport's director of Planning & Environmental Management, said in a news release.

Specifically, the airport expects the system to cut fuel use by 5 million gallons, saving airlines more than $15 million a year, cutting emissions of carbon dioxide by 40,000 metric tons and of nitrogen oxides by 73 tons, and eliminating noise from auxiliary engines running at gates.

Sea-Tac noted that it gets about 90 percent of its power from hydro-electric dams and 10 percent from renewable energy and nuclear sources, meaning the power used to generate the pre-conditioned air is greener than that from airplane engines.

Air conditioning comes from an ethylene-glycol solution cooled by four 750-ton chillers. Alternately, the airport's steam plant heats water that is piped to gates.

The airport got nearly $22 million in Voluntary Airport Low Emissions Grants from the Federal Aviation Administration for the project, and is covering the remainder of the $43 million cost with Airport Development Funds, which come from fees charged to airlines.

The system is running now at gates on the A and B concourses and the south satellite, and is scheduled to extend to the rest of the gates by the end of the year.